Dental radiographs are made using x-ray examination units suited for dental purposes. Dental x-ray films have been developed for intraoral shots and generally have a plate-like construction and standardized dimensions so that the film can be introduced into the oral cavity.
In one procedure, the film alone is placed within the patient's mouth and held in place proximate the tooth or teeth to be filmed when the patient closes her mouth over the film. It has been determined, however, that proper orientation of the film with respect to the tooth or teeth to be filmed, for example, parallel to the longitudinal axis of the tooth, is required to eliminate distortions, improper focus, and the like.
Therefore, film carriers are used including a back plate for mounting the x-ray film and a bite plate orientated at a right angle to the back plate. The x-ray film is held against the back plate, the film carrier is introduced at the proper location within the patient's mouth, and the patient is instructed to bit down on the bite plate.
There is still a need, however, to assure proper orientation of the X-ray tube with respect to the X-ray film mounted against the back plate. Hence, Furhrmann (U.S. Pat. No. 4,965,885) teaches a film carrier capable of engaging with one end of a guide rod at different locations on the film carrier by means of a plurality of spaced bores in the bite plate. The other end of the connecting rod is slideably received through an orifice in a sighting ring affixed circumferentially around the X-ray cone. The U.S. Pat. Nos. to Updegrave (3,745,344) and Levy (1,947,014) teach similar constructions.
One problem with such constructions, however, is that the X-ray technician is still left with the task of assuring proper a orientation of the film carrier within the patient's mouth and also a proper orientation between the film carrier and the aiming ring. X-ray technicians, although skilled, may not always be able to assure proper orientation of the film carrier in the patient's mouth or proper orientation of the film carrier with respect to the aiming ring as it presently has been constructed in prior art devices.
In prior art devices such as Furhrmann, two positioning procedures must be performed. First, the guide rod must be placed in the proper bore in the biting plate; second, the guide rod must be properly positioned within the aiming ring to assure the correct distance between the X-ray cone and the film. If the doctor orders X-rays of the upper right, lower left and anterior portions of the patient's mouth, it may not always be readily apparent to the technician which arrangements and configurations are proper for best filming. Worst, once the proper adjustments are made, realignment may be needed if the patient moves his head or the guide rod improperly moves with respect to the aiming ring. Improper film orientation resulting from the use of such devices is inefficient, results in unnecessary radiation exposure, and patient discomfort. The technician may not be aware of movement resulting in improper exposures, and the need for additional X-rays may not be known until the x-ray plates are exposed.
Another, related problem is that prior art devices may require a separate uniquely configured aiming ring for each film holder. This adds to the overall expense of prior art systems, and also increases the possibility of confusion in matching the correct film holder with the correct aiming ring.